Today I spent some time to make dzlib compile with all Delphi versions from 2007 to XE6 (XE7 to come later). It didn’t take too long since it already supported 2007, XE2 and XE6.

It’s interesting to see, how the RTL evolved between these versions. Some examples:

The IsWhitespace function started out as a class method of TCharacter, then moved to TCharHelper and finally ended up as a method of the Char type itself (probably added through a class helper, I didn’t check).

The global DecimalSeparator variable was marked deprecated for a long time (replaced by a property of the global FormatSettings class) and has finally been removed from the RTL.

There is also a breaking change in the Delphi XE6 RTL:
You can no longer create a TThread suspended and then call Resume/Start from within its constructor. If you do that, you will get an exception. But since the thread no longer gets started until the constructor has run that is no longer necessary.